>> Best I can come up with at the moment is that the engine in my current
>> car
>> is a Mitsubishi "4g64" 2.4L inline 4. -Dave
>
> Really I was just curious if there was anything magical about 40% or
> redline, or if that happened to coincide with the torque peak, which
> I've always heard was a good approximation of where the BSFC map is
> most favorable even under part throttle conditions. Having a nasty
> Real Job(tm) I can't be looking for that info just at the moment
>
> nate
>

Well, I found some numbers for the Nissan 3.5L V6 (aka Maxima) engine. This
engine has been one of the best automotive engines in the world for several
years, so I think it's a good "example" to use.

Redline is 8000, so maximum fuel efficiency should be about 3200RPM, for
that particular Otto Cycle engine (8000 X .4). Peak horsepower is 265 at
5800RPM and peak torque is 255 at 4400RPM. Nissan does use variable valve
timing, but this would tend to favor lower RPMs, as higher RPMs don't need
the valve timing trick to produce more power or torque.

SO, peak fuel efficiency RPM for that particular Otto Cycle engine seems to
be below -both- the horsepower and torque peaks, which makes sense. You
don't need MAXIMUM horsepower or torque to keep a car moving, but more
torque will be helpful for acceleration.

Now I want to hear from Nissan Maxima 3.5L owners . . . what speed (MPH) is
equivalent to 3200RPM engine speed in your Nissan Maxima in top gear (O/D
enabled, if it's an automatic)? If you pay attention to RPM or MPH, have
you noticed an increase in fuel efficiency at that speed??? Since it's an
Otto Cycle engine with an 8000RPM redline, it should be most fuel efficient
around 3200RPM (8000 X .4). IS IT most fuel-efficient near 3200 RPM? -Dave